Prior known power clamps or grippers typically include a pneumatic or hydraulic differential pressure motor with a cylinder housing fixedly mounted to a support structure. At the forward or rod end of the cylinder housing, a clamp arm or gripper jaw mounting structure is connected to the cylinder housing to support movement of at least one clamp arm or gripper jaw connected to the piston rod of the motor. The jaw or clamp arm is pivoted to an open position in response to reciprocal movement of the piston rod in one direction, and is driven to a closed work piece gripping position in response to reciprocal movement of the piston rod in the opposite direction. Typical configurations of known power clamps can be seen in U.S. Pat. Nos. 5,152,568 and 3,599,957. U.S. Pat. No. 5,152,568 discloses a gripper jaw driven through a linkage assembly, while U.S. Pat. No. 3,599,957 discloses a clamp arm driven through cam rollers connected to a rod and moveable in angular slots in the arm to pivot the arm.
It is also known to provide a mounting bracket rotatably mounted on the support with a pair of pivotally mounted plates each having a clamping arm and a cam track. The mounting bracket is known to include an annular shoulder engaging the support, where a flange draws the shoulder against the support to thereby selectively lock the bracket and the piston and cylinder against rotation in any of a plurality of rotational positions.